9.5 平衡二叉树

9.5 平衡二叉树

http://codeup.hustoj.com/contest.php?cid=100000614

A 二叉排序树

题目解析

注意函数L、R、insert的写法，⚠️有&

❗️不要在search返回true/false，这里WA了半天，这样最终只能返回false，大概因为search本身就是递归的

代码

#include <cstdio>
#include <algorithm>

using namespace std;
struct node {
    int data;
    int height;
    node *lchild;
    node *rchild;
};

int getHeight(node *root) {
    if (root == NULL) return 0;
    return root->height;
}

//结点的高度等于左右子树的最大高度+1 ⚠️要加1！！！
void updateHeight(node *root) {
    root->height = max(getHeight(root->lchild), getHeight(root->rchild)) + 1;
}

//平衡因子 = 左右子树高度差
int getBananceFactor(node *root) {
    return getHeight(root->lchild) - getHeight(root->rchild);
}

void R(node *&root) {  //注意&
    node *temp = root->lchild;
    root->lchild = temp->rchild;
    temp->rchild = root;
    updateHeight(root);
    updateHeight(temp);
    root = temp;
}

void L(node *&root) { //注意&
    node *temp = root->rchild;
    root->rchild = temp->lchild;
    temp->lchild = root;
    updateHeight(root);
    updateHeight(temp);
    root = temp;
}

void insert(node *&root, int x) {
    if (root == NULL) {
        root = new node;
        root->data = x;
        root->height = 1;
        root->lchild = root->rchild = NULL;
        return;
    }
    //往左子树插，导致左子树高度>右子树高度
    if (x <= root->data) {
        insert(root->lchild, x);
        updateHeight(root);
        if (getBananceFactor(root) == 2) {
            if (getBananceFactor(root->lchild) == 1) { //LL
                R(root);
            } else if (getBananceFactor(root->lchild) == -1) { //LR
                L(root->lchild);
                R(root);
            }
        }
    } else {
        insert(root->rchild, x);
        updateHeight(root);
        if (getBananceFactor(root) == -2) {
            if (getBananceFactor(root->rchild) == -1) { //RR
                L(root);
            } else if (getBananceFactor(root->rchild) == 1) { //RL
                R(root->rchild);
                L(root);
            }
        }
    }
}

node *create(int n) {
    node *root = NULL;
    int temp;
    for (int i = 0; i < n; i++) {
        scanf("%d", &temp);
        insert(root, temp);
    }
    return root;
}

void search(node *root, int x) {
    if (root == NULL) {
        printf("0");
        return;
    }
    if (x == root->data) {
        printf("1");
        return;
    } else if (x < root->data) search(root->lchild, x);
    else search(root->rchild, x);
}

void preOrder(node *root) {
    if (root == NULL) return;
    preOrder(root->lchild);
    preOrder(root->rchild);
}

void inOrder(node *root) {
    if (root == NULL) return;
    inOrder(root->lchild);
    inOrder(root->rchild);
}

int main() {
    int n, k, temp;
    while (scanf("%d%d", &n, &k) != EOF) {
        node *root = create(n);
        for (int i = 0; i < k; i++) {
            scanf("%d", &temp);
            search(root, temp);
            if (i < k - 1) printf(" ");
            else printf("\n");
        }
    }
    return 0;
}